Process for the manufacture of metal carbonyls



United States Patent Ofiice Patented Sept. 11, 1962 3,053,623 PROCES FOR THE MANUFACTURE OF METAL CARBONYLS Harold E. Podail and Hyrnin Shapiro, Baton Rouge, La.,

assignors to Ethyl Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed July 29, 1.960, Ser. No. 46,087 9 Claims. (Cl. 23-203) This invention relates to the manufacture of metal carbonyls of the group Vl-B metals of the periodic table. Where the term periodic table is used herein, reference is made to The Periodic Chart of the Elements, copyright 1957 and revised 1958 by The Fisher Scientific Company, Chicago, Illinois.

The group VI-B metal carbonyls, chromium, molyb denum and tungsten hexacarbonyl, have been known for a long period of time. There have been several methods published in the literature for the production of these metal carbonyls. One particular method was described (Brimm et al., US. Patent 2,803,525) where an iodide salt of a group VI-B metal was reacted in an oxygenated aliphatic medium with a reducing metal higher than platinum in the electromotive series, i.e., magnesium, sodium, and the ilke, and carbonylation effected by the use of a carbon monoxide atmosphere. According to the patentees it was necessary to use, or form in situ, the iodide salt in order to effect the reaction. Iodine and iodides are expensive and therefore this process is not as economical as would be desirable. Other methods of preparation of the group VI-B metal carbonyls involved the use of a Grignard reagent as a reducing agent in the presence of carbon monoxide to form the metal carbonyl. These processes have also proven undesirable from the standpoint of economy.

It is an object of this invention to provide an economical method for the preparation of metal carbonyls of group VI-B in the periodic table, i.e., chromium, molybdenum and tungsten. It is a further object of this invention to provide an effective process which is simple in operation and one in which the reactants are inexpensive and plentiful. It is also an object of this invention to provide a process free from the shortcomings experienced in processes invented heretofore. Other objects of this invention will be patently obvious from the following descriptions and claims.

The above and other objects of this invention are achieved by reacting a group VI-B metal halogen salt preferably a chloridewith apolycyclic aromatic alkali metal complex in an anhydrous inert diluent in an atmosphere of carbon monoxide at superat-mospheric pressure sufiicient to result in an up-take of carbon monoxide and then hydrolyzing the reaction product. The halide salts of the group Vl-B metals are fluorine, chlorine, bromine and iodine. The most common and preferred halide salts are chromium trichloride, molybdenum pentachloride and tungsten hexachloride. However, other group VI-B metal halide salts, such as CrCl CrBr M01 MoF M0013, MQCL}, M0016, WCl2, WF3, WC14, WC15, and like can be used. These salts are usually employed in the anhydrous form since water adversely affects the reaction forming the metal carbonyls.

The polycyclic aromatic alkali metal complex is produced from any of the polycyclic aromatic hydrocarbons capable of forming the so-called addition compounds with an alkali metal. Examples of the polycyclic aromatic hydrocarbons are biphenyl, anthracene, phenanthrene and naphthalene. Without desiring to be bound by any theoretical considerations, it definitely appears that the actual reducing agent in the polycyclic aromatic alkali metal complex is the polycyclic aromatic hydrofree polycyclic aromatic hydrocarbon.

carbon carbanion and not the "alkali metal cation. This is in accord with the theory described by De Paul, Lipkin and Weisman in an article in volume 78, J.A.C.S., page 116 (1956) to the effect that in these alkali metal complexes the metal exists as a cation and the ring system exists as an anion. Examples of the polycyclic aromatic alkali metal complex are sodium biphenyl complex, potassium biphenyl complex, lithium biphenyl complex, sodium anthracene complex, rubidium anthracene complex, lithium anthracene complex, sodium phenanthrene complex, sodium naphthalene complex, lithium naphthalene complex, cesium naphthalene complex, and the like. From a cost-effectiveness standpoint, the complexes of sodium are the most efficient and hence are preferred. These polycyclic aromatic alkali metal complexes are prepared by reacting the alkali metal directly With'the aromatic hydrocarbon in the presence of a diluent. There have been numerous examples and methods described in the literature for the preparation of these aromatic hydrocarbon alkali metal addition compounds, some of which are US. Patents 2,019,832, 2,023,793, 2,125,401, 2,146,447 and 2,150,039.

An especially important feature of this invention is the fact that the process takes place at a low temperature.- While the process can be run over a broad range of temperatures from about 20 C. to 100 C., the more especially preferred temperatures range from below about 0 C. to about 30 C. A very significant feature, then, is that this reaction can take place at room temperature with great efficiency. Consequently, there is no need to encumber the reaction equipment with elaborate and costly heating or refrigerating means.

The inert diluents which can be used in the process of this invention are those in which the polycyclic aromatic alkali metal complex is soluble. Examples of these inert solvents are hydrocarbons, amines, and, preferably, ethers. Polyethers are particularly preferred, especially the diethylene glycol dialkyl ethers.

It is important that this reaction take place in an atmosphere of carbon monoxide at superatmospheric pressure. The precise pressures at which there is a carbon monoxide uptake are dependent upon the particular reactants and reaction temperatures used. In general, however, the pressure can be from about 300 p.s.i. to about 10,000 p.s.i. The more particularly referred pressure, however, is from about 800 p.s.i. to about 3500 p.s.i.

The reaction product can be hydrolyzed under a variety of atmospheres such as air or carbon monoxide in a' dilute aqueous mineral acid at a temperature from about 0 C. to 30 C. One feature of this process is the fact that the product can be hydrolyzed in the presence ofair and at room temperature.

One of the most unique features of this process is the.

process of this invention it definitely appears that the.

negative polycyclic aromatic hydrocarbon radical reduces the group VIB metal halogen salt thus freeing the group VIB metal to react with carbon monoxide, thereby forming the metal hexacarbonyl. In this process the negative,

polycyclic aromatic hydrocarbon radical is oxidized to a This is very vividly demonstrated by the fact that the polycyclic aro- Among the numerous advantages of this process is the fact that the reagents may be contacted above C. with out excessive over-reduction of the group VI-B metal halogen to the metal state. Such over-reduction is characteristic of certain prior processes and is disadvantageous in that the metal so reduced is in such form as it does not react to form the carbonyl. Another advantage of this invention is the fact that the reducing agent may be pumped in solution to the reactor containing the group VI-B metal halide and the carbon monoxide. This is an especially good feature since metallic molten sodium is difiicult to pump under pressure. Sodium in the molten state tends to agglomerate and thus hinder the reaction.

The process of this invention will be more fully understood by reference to the following examples in which all parts are by Weight unless otherwise specified.

Example I Anhydrous chromium trichloride (3.2 parts) in 120 parts by volume of diethylene glycol dimethyl ether, as an inert solvent, was reacted with 18 parts of 1:1 sodium naphthalene complex under a pressure of 3500 p.s.i. of carbon monoxide at 25 C. for 18 hours. To the reaction mixture was added 50 parts by volume of 6 molar hydrochloric acid under 800 p.s.i. of carbon monoxide over a period of 2 hours at 0 C. The product recovered was chromium hexacarbonyl.

Example II Anhydrous chromium trichloride (3.2 parts) in 120 parts by volume of diethylene glycol dimethyl ether was reacted with 18 parts of 1:1 sodium naphthalene complex under a pressure of 3500 p.s.i. of carbon monoxide at 100 C. for 6 hours. This product was hydrolyzed with 50 parts by volume of 3 molar hydrochloric acid at 25 C. in air. The product recovered was chromium hexacarbonyl.

Example III Chromium trichloride (1.6 parts) is reacted with 5.3 parts of 1:1 sodium biphenyl complex in 30 parts of diethylene glycol butyl ether under a pressure of 1500 p.s.i. of carbon monoxide at 20 C. for 6 hours. The product is hydrolyzed and recovered as in Example I. The product is chromium hexacarbonyl.

Example 1V Molybdenum pentachloride (2.7 parts) is reacted with 14 parts of 1:1 sodium anthracene complex in 30 parts tetrahydropyran in the same manner as Example I. The product which is obtained is molybdenum hexacarbonyl.

Example V Tungsten hexachloride (4 parts) is reacted with 16 parts of 1:1 sodium phenanthrene complex in 35 parts anisole under a pressure of 1000 p.s.i. of carbon monoxide at 25 C. for hours. The product is hydrolyzed with 25 parts by volume of 6 normal sulfuric acid at 25 C. in the presence of carbon monoxide. The product recovered is tungsten hexacarbonyl.

Example VI Chromium trichloride (3.2 parts) is reacted with 18 parts 1:1 sodium naphthalene complex in the presence of 120 parts tetrahydrofuran under a pressure of 800 p.s.i. of carbon monoxide at 20 C. for 14 hours. The product is hydrolyzed with 50 parts by volume 6 molar acetic acid at 25 C. in the presence of carbon monoxide. The product recovered is chromium hexacarbonyl.

Example VII Molybdenum pentachloride (2.7 parts) is reacted with 11 parts 1:1 sodium naphthalene complex in the presence of the 35 parts of isopropyl ether under a pressure of 1200 p.s.i. of carbon monoxide at 24 C. for 8 hours.

The product is hydrolyzed with 30 parts by volume 6 normal phosphoric acid at 25 C. in the presence of carbon monoxide. The product recovered is molybdenum hexacarbonyl.

Example VIII To 3.2 parts chromium trichloride is added 120 parts of triethylene glycol dimethyl ether under- 1,000 p.s.i. of carbon monoxide. 1:1 sodium naphthalene complex (8 parts) is pumped into the reactants over a period of 3 hours at 65 C. For recovery of the product, the reactants are cooled to 25 C. and 50 parts by volume of 6 molar aqueous hydrochloric acid is pumped in under 800 p.s.i. of carbon monoxide over a period of 2 hours. To this is added parts by volume of Water and the chromium hexacarbonyl is separated and recovered by steam distillation.

It will be noticed that in the preceding examples the term 1:1 was used in conjunction with the alkali metal polycyclic aromatic hydrocarbon complex. This means that the ratio of the alkali metal is one gram atom to one.

mole of the polycyclic aromatic hydrocarbon.

The temperature at which the reaction is conducted is critical in order to obtain high yields of the desired metal carbonyl. Thus, the reaction should be carried out from about 20 C. to about 100 C. A more preferred temperature range is from below about -0 C. to about 30 C. At temperatures above 70 C. the yield of the desired metal carbonyl is appreciably diminished.

The time of the reaction depends on other conditions under which the reaction is conducted, especially temperature and solvents, although times between a few minutes and several hours are generally quite adequate. It is usually preferred to conduct the reaction for a period of from about 45 minutes to about 18 hours.

The proportions of the reactants can also be varied and are generally based upon the amount and particular metal salt of the group VI-B metal halides present. The mole ratio between the alkali metal polycyclic aromatic complex and the group VI-B metal halide salt ranges from about 2:1 to about 8:1. The optimum mole ratio between the alkali metal polycyclic hydrocarbon complex and chromium halides ranges between about 2:1 to about 6: 1. In the case of chromium trihalides, the more preferred mole ratio is from 3:1 to 5:1. The optimum mole ratio between alkali metal hydrocarbon complexes and molybdenum salts ranges from about 3:1 to about 7:1 'while the more preferred mole ratio is from 5:1 to 7:1. The optimum mole ratio between the alkali metal complex and the tungsten halide salts is from about 2:1 to about 8:1 while the more preferred range is from about 6:1 to about 8:1. It should be noted that where an inordinate amount of the alkali metal hydrocarbon complex is used an excessive reduction of the metal halide to free metal could result thus impairing the reaction.

The reducing agents which can be employed in this invention are polycyclic aromatic hydrocarbons which will form the so-called addition compounds with the alkali metals. The polycyclic aromatic hydrocarbons which may be reacted with the alkali metals to form the aromatic alkali metal complex are naphthalene, biphenyl, phenanthrene, acenaphthene, anthracene, retene, as Well as homolog (e.g., alkyl derivatives) of these hydrocarbons.

The inert diluents which may be used are any inert hydrocarbon compounds. The more particularly preferred diluents, however, are those in which the alkali metal complex is soluble. The polyethers are particularly desirable as diluents in this process. Typical examples of suitable ethers are diethyl ether, diisopropyl ether, dibutyl ether, methylphenyl ether (anisole), phenyl ether, p-tolyl ether, ethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether and other alkyl ethers containing from 1 to 10 carbon atoms per alkyl group.

Cyclic ethers such as tetrahydrofuran, tetrahydropyran and dioxane can also be used. Other examples of diluents are pyridine, triethylamine, mesitylene, toluene, piperidine, and the like.

The hydrolytic agents capable of being used in the hydrolytic carbonylation step of this process can be selected from a broad group of compounds. These hydrolytic agents must be capable of donating a hydrogen ion. A few examples of these hydrolytic agents are water, methyl alcohol, ethyl alcohol, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and the like. It will be noted that the acids used in this hydrolysis are not oxidizing acids. In general, dilute aqueous mineral acids are useful for this purpose. The more preferred and cheaper hydrolytic agent is hydrochloric acid which can be used either in a gaseous state or in an aqueous solution.

This process provides products which are of considerable use. These products can be subjected to high temperatures, thereby providing decomposition to obtain the respective metals in a finely divided form. For example, when molybdenum carbonyl is heated at a temperature above 250 C. in an inert atmosphere, a finely divided pyrophoric product is obtained which is useful in electronic tubes for anodes and support members or in alloying in making steels. The carbonyls of the metals chromium, molybdenum and tungsten and mixtures thereof or with other carbonyls, in various atmospheres, can be decomposed on metal surfaces, such as steel to give resistant coatings, which are stable at high temperatures. These valuable metals can also be produced in extremely pure form and are suificiently ductile for structural purposes as in aircraft fabrication. These products are also useful as chemical intermediates in preparing organometallic compounds.

Having thus described the process of this invention it is not intended that it be limited except as set forth in the following claims.

We claim:

1. A process for the manufacture of carbonyls of the metals of group VIB of the periodic table of the elements having atomic numbers from 24 to 74, inclusive, which comprises reacting a metal halogen salt of a group VI-B metal having an atomic number from 24 to 74, in-

elusive, with an addition product between a polycyclic aromatic hydrocarbon and an alkali metal, the hydro carbon portion existing as a carbanion and the alkali metal existing in the +1 valence state, the reaction being conducted in an inert solvent and in an atmosphere of carbon monoxide at a superatmospheric pressure sufiicient to result in an uptake of carbon monoxide, the mole ratio between the said addition product and the metal halogen salt ranging from about 2:1 to about 8:1; and then hydrolyzing the reaction mixture.

2. The process of claim 1 wherein the alkali metal of the polycyclic aromatic hydrocarbon addition product is sodium.

3. The process of claim 1 wherein the inert solvent is an ether.

4. The process of claim 1 wherein the solvent is a diethylene glycol dialkyl ether.

5. The process of claim 1 wherein the halogen of the metal halogen salt of the group VI-B metal is chlorine.

6. The process of claim 1 wherein the metal halogen salt of the group VI-B metal is chromium trichloride.

7. The process of claim 1 wherein the metal halogen salt of the group VI-B metal is molybdenum pentachloride.

8. The process of claim 1 wherein the metal halogen salt of the group VI-B metal is tungsten chloride.

9. A process for the manufacture of chromium hexacarbonyl which comprises reacting chromium trichloride with a sodium-naphthalene addition product and carbon monoxide in a diethylene glycol alkyl ether solvent at a temperature from about -20 C. to about 30 C. and at a pressure from about 800 to about 3500 psi, the mole ratio between the said addition product and the chromium trichloride ranging from about 2:1 to about 8:1; and then hydrolyzing the reaction mixture with dilute aqueous mineral acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,880,066 Closson et al. Mar. 31, 1959 2,880,067 Closson et a1 Mar. 31, 1959 2,952,521 Podall Sept. 13, 1960 2,952,523 Podall Sept. 13, 1960 2,952,524 Podall et al. Sept. 13, 1960 

1. A PROCESS FOR THE MANUFACTURE OF CARBONYLS OF THE METALS OF GROUP VI-B OF THE PERIODIC TABLE OF THE ELEMENTS HAVING ATOMIC NUMBERS FROM 24 TO 74, INCLUSIVE, WHICH COMPRISES REACTING A METAL HALOGEN SALT OF A GROUP VI-B METAL HAVING AN ATOMIC NUMBER FROM 24 TO 74, INCLUSIVE, WITH AN ADDITION PRODUCT BETWEEN A POLYCYCLIC AROMATIC HYDROCARBON AND AN ALKALI METAL, THE HYDROCARBON PORTION EXISTING AS A CARBANION AND THE ALKALI METAL EXISTING IN THE +1 VALENCE STATE, THE REACTION BEING CONDUCTED IN AN INERT SOLVENT AND IN AN ATMOSPHERE OF CARBON MONOXIDE AT A SUPERATMOSPHERIC PRESSURE SUFFICIENT TO RESULT IN AN UPTAKE OF CARBON MONOXIDE, THE MOLE RATIO BETWEEN THE SAID ADDITION PRODUCT AND THE METAL HALOGEN SALT RANGING FROM ABOUT 2:1 TO ABOUT 8:1; AND THEN HYDROLYZING THE REACTION MIXTURE. 